This is a REALLY good debate and nothing that will ever get settled as there will always be people with different opinions.
I just want to know, why does this have to be an either/or thing? It sounds like if newer cars are present, older cars can't be there or for every new vehicle there, it's taking up a spot where an older vehicle would normally be.
If 100 vintage cars show up to a car show and there are also 200 newer cars there, there are still 100 vintage cars there. If only vintage cars were allowed, there would still be 100 vintage cars there. Just because newer vehicles are allowed, doesn't mean there will be less older vehicles. It just means the car show is bigger. Yes, if newer vehicles are allowed, some older cars may not come, BUT if newer vehicles are allowed, it may also bring out some more older vehicles as car guys with old cars probably have a friend with a newer car and are more willing to go if they car go with a friend instead of sitting by themselves. I don't know anyone in my circle of friends with a 60's car so I'm not going to go to a show with other older vehicles and hang out by myself, but I do know lots of people with newer Corvettes and would gladly go to a show if they went too.
Two things I would like to see. Parking preference given to older vehicles, and if there is limited parking, then only allowing older vehicles.